Telecommunications jack with crosstalk compensation and arrangements for reducing return loss

ABSTRACT

The present disclosure relates to a telecommunications jack including a housing having a port for receiving a plug. The jack also includes a plurality of contact springs adapted to make electrical contact with the plug when the plug is inserted into the port of the housing, and a plurality of wire termination contacts for terminating wires to the jack. The jack further includes a circuit board that electrically connects the contact springs to the wire termination contacts. The circuit board includes a crosstalk compensation arrangement for reducing crosstalk at the jack. The circuit board also includes arrangements that reduce return loss at the jack.

TECHNICAL FIELD

The present invention relates generally to telecommunications equipment.More particularly, the present invention relates to telecommunicationsjacks that are configured to compensate for near end crosstalk.

BACKGROUND

In the field of data communications, communications networks typicallyutilize techniques designed to maintain or improve the integrity ofsignals being transmitted via the network (“transmission signals”). Toprotect signal integrity, the communications networks should, at aminimum, satisfy compliance standards that are established by standardscommittees, such as the Institute of Electrical and ElectronicsEngineers (IEEE). The compliance standards help network designersprovide communications networks that achieve at least minimum levels ofsignal integrity as well as some standard of compatibility.

One prevalent type of communication system uses twisted pairs of wiresto transmit signals. In twisted pair systems, information such as video,audio and data are transmitted in the form of balanced signals over apair of wires. The transmitted signal is defined by the voltagedifference between the wires.

Crosstalk can negatively affect signal integrity in twisted pairsystems. Crosstalk is unbalanced noise caused by capacitive and/orinductive coupling between wires and a twisted pair system. The effectsof crosstalk become more difficult to address with increased signalfrequency ranges.

The effects of crosstalk also increase when transmission signals arepositioned closer to one another. Consequently, communications networksinclude areas that are especially susceptible to crosstalk because ofthe proximity of the transmission signals. In particular, communicationsnetworks include connectors that bring transmission signals in closeproximity to one another. For example, the contacts of traditionalconnectors (e.g., jacks and plugs) used to provide interconnections intwisted pair telecommunications systems are particularly susceptible tocrosstalk interference.

FIG. 1 shows a prior art panel 20 adapted for use with a twisted pairtelecommunications system. The panel 20 includes a plurality of jacks22. Each jack 22 includes a port 24 adapted to receive a standardtelecommunications plug 26. Each of the jacks 22 is adapted to beterminated to four twisted pairs of transmission wires. As shown at FIG.2, each of the jacks 22 includes eight contact springs labeled as havingpositions 1-8. In use, contact springs 4 and 5 are connected to a firstpair of wires, the contact springs 1 and 2 are connected to a secondpair of wires, contact springs 3 and 6 are connected to a third pair ofwires, and contact springs 7 and 8 are connected to a fourth pair ofwires. As shown at FIG. 3, a typical plug 26 also has eight contacts(labeled 1-8) adapted to interconnect with the corresponding eightcontacts of the jack 22 when the plug is inserted within the port 24.

To promote circuit density, the contacts of the jacks and the plugs arerequired to be positioned in fairly close proximity to one another.Thus, the contact regions of the jacks and plugs are particularlysusceptible to crosstalk. Furthermore, certain pairs of contacts aremore susceptible to crosstalk than others. For example, the first andthird pairs of contacts in the plugs and jacks are typically mostsusceptible to crosstalk.

To address the problems of crosstalk, jacks have been designed withcontact spring configurations adapted to reduce the capacitive couplinggenerated between the contact springs so that crosstalk is minimized. Analternative approach involves intentionally generating crosstalk havinga magnitude and phase designed to compensate for or correct crosstalkcaused at the plug or jack. Typically, crosstalk compensation can beprovided by manipulating the positioning of the contacts or leads of thejack or can be provided on a circuit board used to electrically connectthe contact springs of the jack to insulation displacement connectors ofthe jack.

The telecommunications industry is constantly striving toward largersignal frequency ranges. As transmission frequency ranges widen,crosstalk becomes more problematic. Thus, there is a need for furtherdevelopment relating to crosstalk remediation.

SUMMARY

One aspect of the present disclosure relates to circuit board layeringconfigurations adapted for supporting the effective compensation ofcrosstalk in a telecommunications jack.

Another aspect of the present disclosure relates to the use of highimpedance lines to compensate for return loss caused by crosstalkcompensation arrangements.

Still another aspect of the present disclosure relates to the use ofcapacitive couplings to overcome return loss issues caused by crosstalkcompensation arrangements.

Still another aspect of the present disclosure relates to crosstalkcompensation arrangements and methods for designing crosstalkcompensation arrangements.

A variety of additional inventive aspects will be set forth in thedescription that follows. The inventive aspects can relate to individualfeatures and to combinations of features. It is to be understood thatboth the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the broad inventive concepts upon which the embodiments disclosedherein are based.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art telecommunications panel;

FIG. 2 is a schematic illustration of a prior art jack;

FIG. 3 is a schematic representation of a prior art telecommunicationsplug;

FIG. 4 is a front, perspective view of a telecommunications jack havingfeatures that are examples of inventive aspects in accordance with theprinciples of the present disclosure;

FIG. 5 is an exploded view of the jack of FIG. 4;

FIG. 6 is a side view of the circuit board, insulation displacementconnectors and contact springs of the telecommunications jack of FIG. 4;

FIG. 7 is a front view of the circuit board, contact springs andinsulation displacement connectors of FIG. 6;

FIG. 8 is a top view of the circuit board and contact springs of FIG. 6;

FIG. 9 is a cross-sectional view taken along section line 9-9 of FIG. 8;

FIG. 10 is a schematic diagram showing a crosstalk compensation schemeincorporated into the telecommunications jack of FIG. 4;

FIG. 11 is a schematic diagram showing a compensation arrangement usedto provide crosstalk compensation between the 4-5 and 3-6 pairs of thetelecommunications jack of FIG. 4;

FIG. 12 is a schematic vector diagram showing a compensation arrangementused to provide crosstalk compensation between the 1-2 and 3-6 pairs ofthe telecommunications jack of FIG. 4;

FIG. 13 is a graph that depicts how certain factors can affect returnloss in the jack of FIG. 4 across a range of frequencies;

FIG. 14 is a tracing overlay view of the circuit board used in thetelecommunications jack of FIG. 4;

FIG. 15 shows a front conductive layer of the circuit board used in thetelecommunications jack of FIG. 4;

FIG. 16 shows a middle conductive layer of the circuit board used in thetelecommunications jack of FIG. 4; and

FIG. 17 is shows a back conductive layer of the circuit board used inthe telecommunications jack of FIG. 4.

DETAILED DESCRIPTION

FIGS. 4 and 5 show a telecommunications jack 120 (i.e., atelecommunications connector) having features that are examples ofinventive aspects in accordance with the principles of the presentdisclosure. The jack 120 includes a dielectric housing 122 having afront piece 124 and a rear piece 126. The front and rear pieces 124, 126can be interconnected by a snap fit connection. The front piece 124defines a front port 128 sized and shaped to receive a conventionaltelecommunications plug (e.g., an RJ style plug such as an RJ 45 plug).The rear piece 126 defines an insulation displacement connectorinterface and includes a plurality of towers 130 adapted to houseinsulation displacement connector blades/contacts. The jack 120 furtherincludes a circuit board 132 that mounts between the front and rearpieces 124, 126 of the housing 122. A plurality of contact springsCS₁-CS₈ are terminated to a front side of the circuit board 132. Aplurality of insulation displacement connector blades IDC₁-IDC₈ areterminated to a back side of the circuit board 132. The contact springsCS₁-CS₈ extend into the front port 128 and are adapted to beelectrically connected to corresponding contacts provided on a plug whenthe plug is inserted into the front port 128. The insulationdisplacement connector blades IDC₁-IDC₈ fit within the towers 130 of therear piece 126 of the housing 122. The circuit board 132 has tracksT₁-T₈ (e.g., tracings, see FIGS. 14-17) that respectively electricallyconnect the contact springs CS₁-CS₈ to the insulation displacementconnector blades IDC₁-IDC₈.

In use, wires are electrically connected to the contact springs CS₁-CS₈by inserting the wires between pairs of the insulation displacementconnector blades IDC₁-IDC₈. When the wires are inserted between pairs ofthe insulation displacement connector blades IDC₁-IDC₈, the blades cutthrough the insulation of the wires and make electrical contact with thecenter conductors of the wires. In this way, the insulation displacementconnector blades IDC₁-IDC₈, which are electrically connected to thecontact springs CS₁-CS₈ by the tracks on the circuit board, provide anefficient means for electrically connecting a twisted pair of wires tothe contact springs CS₁-CS₈ of the jack 120.

The contact springs CS₁-CS₈ are shown more clearly in FIGS. 6-8. Therelative positioning, shape and curvature of the contact springs CS₁-CS₈is preferably adapted to provide some initial crosstalk compensation atthe jack 120.

The circuit board 132 of the jack 120 is preferably a multiple layercircuit board. For example, FIG. 9 shows the circuit board 132 includinga first conductive layer 140, a second conductive layer 142 and a thirdconductive layer 144. The first and second conductive layers 140, 142are separated by a first dielectric layer 146. The second and thirdconductive layers 142, 144 are separated by a second dielectric layer148. The first conductive layer 140 is located at a front side of thecircuit board 132 and the third conductive layer 144 is located at aback side of the circuit board 132. The contact springs CS₁-CS₈ aremounted at the front side of the circuit board 132, while the insulationdisplacement connector blades IDC₁-IDC₈ are mounted at the back side ofthe circuit board 132. Vias extend through the first and seconddielectric layers 146, 148 to provide electrical connections between theconductive layers 140, 142 and 144. The conductive layers 140, 142 and144 are defined by electrically the conductive tracks T₁-T₈ (see FIGS.14-17). The tracks T₁-T₈ are formed (e.g., etched or otherwise provided)on the dielectric layers 146, 148.

The circuit board 132 preferably includes structures for compensatingfor near end crosstalk that occurs at the jack/plug interface. Incertain embodiments, the structures for compensating for near endcrosstalk include capacitive couplings provided between the first andsecond conductive layers 140, 142. In preferred embodiments, thecapacitive couplings are provided by sets of opposing, generallyparallel capacitive plates located at the first and second conductivelayers 140, 142. To increase the magnitude of the capacitive couplingprovided between the capacitive plates of the first and secondconductive layers 140, 142, it is desirable for the first dielectriclayer 146 to be relatively thin. For example, in certain embodiments thefirst dielectric layer 146 can have a thickness t₁ less than about 0.01inches, or less than about 0.0075 inches, or less than about 0.005inches, or less than 0.003 inches. In other embodiments, the thicknesst₁ can be in the range of 0.001 inches to 0.003 inches or in the rangeof 0.001 inches to 0.005 inches. In a preferred embodiment, thethickness t₁ is about 0.002 inches.

In certain embodiments, the first dielectric layer 146 can be made of amaterial having a relatively low dielectric constant. As used herein,dielectric constants are dielectric constants relative to air. Incertain embodiments, the dielectric constant of the first dielectriclayer 146 can be equal to or less than about 5. In other embodiments,the dielectric constant of the first dielectric layer 146 can be lessthan or equal to about 4 or less than or equal to about 3. An examplematerial for manufacturing the first dielectric layer 146 is a flameresistant 4 (FR-4) circuit board material. FR-4 circuit board materialis a composite of a resin epoxy reinforced with a woven fiberglass mat.

The second dielectric layer 148 is preferably configured to isolate thethird conductive layer 144 from the first and second conductive layers140, 142. The second dielectric layer 148 can have a different thicknesst₂ than the thickness t₁ of the first dielectric layer 146. In certainembodiments, the second dielectric layer 148 is at least 2.5 timesthicker than the first dielectric layer 146 or at least five timesthicker than the first dielectric layer 146. In still other embodiments,the second dielectric layer 148 is at least 10 times or at least 20times thicker than the first dielectric layer 146. In one exampleembodiment, the thickness t₂ of the second dielectric layer 148 is inthe range of 0.050 inches to 0.055 inches. In another exampleembodiment, the thickness t₂ of the second dielectric layer 148 is inthe range of 0.040 inches to 0.050 inches.

The second dielectric layer 148 can also be manufactured of a differentmaterial as compared to the first dielectric layer 146. In certainembodiments, the second dielectric layer can have different dielectricproperties as compared to the first dielectric layer 146. For example,in certain embodiments the first dielectric layer 146 can have adielectric constant that is greater (e.g., at least 1.5 times or atleast 2 times greater) than the dielectric constant of the seconddielectric layer 148. In one example, the second dielectric layer 148can be manufactured of a material such as FR-4. Of course, it will beappreciated that other materials could also be used.

The circuit board 132 includes a number of capacitive couplings havingmagnitudes and locations adapted to compensate for near end crosstalk.Near end crosstalk is most problematic between the 4-5 and 3-6 pairs. Tocompensate for near end crosstalk between the 4-5 and 3-6 pairs, threeinterdependent zones of compensation are used between tracks T₄₋₅ andtracks T₃₋₆. As shown at FIG. 10, the three interdependent zones ofcompensation include a first zone of compensation Z_(A1), a second zoneof compensation Z_(A2) and a third zone of compensation Z_(A3). Thefirst zone of compensation Z_(A1) includes a capacitive coupling C1between track T₃ and track T₅, and a capacitive coupling C2 betweentrack T₄ and track T₆. The second zone of compensation Z_(A2) includes acapacitive coupling C3 between track T₃ and track T₄, and a capacitivecoupling C4 between track T₅ and track T₆. The third zone ofcompensation Z_(A3) includes a capacitive coupling C5 between track T₃and track T₅, and a capacitive coupling C6 between track T₄ and trackT₆.

FIG. 11 is a schematic diagram representative of the compensationarrangement used to provide crosstalk compensation between the 4-5 and3-6 pairs. As shown at FIG. 11, the compensation arrangement includes afirst vector 100, a second vector 102, a third vector 104, and a fourthvector 106. The first vector 100 and the third vector 104 have positivepolarities, while the second vector 102 and the fourth vector 106 havenegative polarities. The first vector 100 has a magnitude of M andcorresponds to crosstalk introduced at the plug. The second vector 102has a magnitude of −3M and corresponds to crosstalk introduced at thefirst zone of compensation Z_(A1). The third vector 104 has a magnitudeof 3M and corresponds to crosstalk introduced at the second zone ofcompensation Z_(A2). The fourth vector 106 has a magnitude of −M andcorresponds to crosstalk introduced at the third zone of compensationZ_(A3). It will be appreciated that each vector is a lump sum of thetotal crosstalk provided at each respective compensation zone, with thevectors being placed at the centers or midpoints of the compensationzones.

In designing the compensation scheme of FIG. 11, a number of factors aretaken into consideration when determining the placement of thecompensation zones. One factor includes the need to accommodate signaltravel in both directions (i.e., in forward and reverse directions)through the tracks on the circuit board. To accommodate forward andreverse transmissions through the circuit board, the compensation schemepreferably has a configuration with forward and reverse symmetry. It isalso desirable for the compensation scheme to provide optimizedcompensation over a relatively wide range of transmission frequencies.For example, in one embodiment, performance is optimized for frequenciesranging from 1 MHz to 500 MHz. It is further desirable for thecompensation arrangement to take into consideration the phase shiftsthat occur as a result of the time delays that take place as signalstravel between the zones of compensation.

To minimize the effect of phase shift in the compensation arrangement,it is preferred for the second vector 102 to be positioned as close aspossible to the first vector 100. In FIG. 11, the time delay between thefirst vector 100 and the second vector 102 is shown as x. In one exampleembodiment, x can be about 100 picoseconds for a signal having atransmission speed of 3×10⁸ meters per second.

To maintain forward and reverse symmetry, it is preferred for the timedelay between the third vector 104 and the fourth vector 106 to beapproximately the same as the time delay between the first vector 100and the second vector 102. As shown in FIG. 11, the time delay betweenthe third and fourth vectors is depicted as x.

The time delay y between the second vector 102 and the third vector 104is preferably selected to optimize the overall compensation effect ofthe compensation scheme over a relatively wide range of frequencies. Byvarying the time delay y between the second vector 102 and the thirdvector 104, the phase angles of the first and second compensation zonesare varied thereby altering the amount of compensation provided atdifferent frequencies. In one example embodiment, to design the timedelay y, the time delay y is initially set with a value generally equalto x (i.e., the time delay between the first vector 102 and the secondvector 104). The system is then tested or simulated to determine if anacceptable level of compensation is provided across the entire signalfrequency range intended to be used. If the system meets the crosstalkrequirements with the value y set equal to x, then no further adjustmentof the value y is needed. If the compensation scheme fails the crosstalkrequirements at higher frequencies, the time delay y can be shortened toimprove performance at higher frequencies. If the compensation schemefails the crosstalk requirements at lower frequencies, the time delay ycan be increased to improve crosstalk performance for lower frequencies.It will be appreciated that the time delay y can be varied withoutaltering forward and reverse symmetry.

It has been determined that when magnitudes of the second and thirdvectors 102, 104 are respectively −3M and 3M, the distance y ispreferably greater than the distance x to provide optimized crosstalkcompensation. However, if the magnitudes of the vectors 102, 104 arereduced below −3M and 3M (e.g., to −2.7M and 2.7M), the distance y ispreferably less than the distance x to provide optimized crosstalkcompensation.

Crosstalk can also be an issue between the 1-2 and 3-6 pairs.Particularly, substantial crosstalk can be generated between track T₂and track T₃. As shown at FIG. 10, a two-zone compensation arrangementis used to compensate for this crosstalk. The two-zone compensationarrangement includes a first zone of compensation Z_(B1) and a secondzone of compensation Z_(B2). The first zone of compensation Z_(B1)includes a capacitive coupling C7 between track T₁ and track T₃, and acapacitive coupling C8 between track T₂ and track T₆. The second zone ofcompensation Z_(B2) includes a capacitive coupling C9 between track T₁and track T₆. FIG. 12 is a schematic vector diagram showing thecompensation arrangement used between the 1-2 and 3-6 pairs. As shown atFIG. 12, three crosstalk vectors are taken into consideration. The firstcrosstalk vector 110 is representative of crosstalk generated at theplug. A second vector 112 is representative of crosstalk provided at thefirst compensation zone Z_(B1). The third vector 114 is representativeof crosstalk generated at the second compensation zone Z_(B2). The firstand third vectors 110, 114 have positive polarities and magnitudes ofabout N. The second vector 112 has a negative polarity and a vectorabout 2N. In testing the compensation arrangement provided betweentracks 1-2 and 3-6, it was determined that improved results wereobtained when no discrete capacitive coupling was provided between thetrack T₂ and track T₃ at the second zone of compensation Z_(B2).However, in alternative embodiments, a discrete capacitive coupling canalso be provided between track T₂ and track T₃ to maintain symmetry. Itwill be appreciated that M (shown at FIG. 11) is typically substantiallygreater in magnitude than N (shown at FIG. 12).

A two-zone compensation arrangement can be also be used to providecrosstalk compensation between the 4-5 and 7-8 pairs. For example, FIG.10 depicts a first zone of compensation Z_(C1) and a second zone ofcompensation Z_(C2) providing compensation between the 4-5 and 7-8pairs. The first zone of compensation Z_(C1) includes a capacitivecoupling C10 between track T₈ and track T₅. The second zone ofcompensation Z_(C2) includes a capacitive coupling C11 between tracks 8and 4. The first and second zones of compensation Z_(C1) and Z_(C2) canhave a 1-2-1 magnitude sequence similar to the two-zone compensationarrangement described with respect to tracks 1-2 and 3-6.

In addition to the multiple zone compensation arrangements describedabove, a number of single zone compensations can also be used. Forexample, zone Z_(D1) is a single zone compensation including acapacitive coupling C12 provided between track T₂ and track T₅. Anothersingle zone compensation Z_(E1) is provided by a capacitive coupling C13formed between track T₆ and track T₈. Another capacitive coupling C14between track T₅ and track T₆ compensates for unintended crosstalkgenerated within the board itself.

To address the crosstalk issue between the 4-5 and 3-6 pairs, arelatively large amount of capacitance is used. This large amount ofcapacitance can cause the jack to have unacceptable levels of returnloss. A number of methods can be used to improve return lossperformance. For example, return loss performance can be improved byincreasing the impedance of tracks T₃, T₄, T₅ and T₆ of the board. Theimpedance of the tracks is preferably increased through the first,second and third zones of compensation, and also after the first,second, and third zones of compensation. The impedance can be increasedby minimizing the transverse cross sectional area of tracks T₃, T₄, T₅and T₆. An example transverse cross-sectional area of the tracks is inthe range of 13 to 16 square mils (1 mil=0.001 inches). The impedancecan also increase by routing the tracks so as to maintain a relativelylarge spacing between tracks T₃ and T₄ and between tracks T₅ and T₆. Inone embodiment, the impedance of the tracks T₃-T₆ is greater than 100Ohms. In another embodiment, the impedance is equal to or greater than120 Ohms. In still another embodiment, the impedance of the tracks T₃-T₆is equal to or greater than 150 Ohms. In still a further embodiment, theimpedance of the tracks T₃-T₆ is equal to or greater than 175 Ohms. In afurther embodiment, the impedance of the tracks T₃-T₆ is equal to orgreater than 200 Ohms.

The impedance of tracks T₃-T₆ can also be increased by increasing thelengths of the tracks T₃-T₆ provided between the springs CS₃-CS₆ and theinsulation displacement connectors IDC₃-IDC₆. In certain embodiments,this increased length can be provided by using serpentine or loop backrouting configurations for the tracks T₃-T₆. In lengthening the tracksT₃-T₆ provided between contact springs CS₃-CS₆ and their correspondinginsulation displacement connector blades IDC₃-IDC₆, in certainembodiments, the tracks T₃-T₆ can be lengthened to be at least one and ahalf times or at least two times as long as the straight line distancebetween the springs CS₃-CS₆ and their corresponding insulationdisplacement connector blades IDC₃-IDC₆. In other embodiments, thetracks T₃-T₆ can be at least three or four times as long as the straightline distances between the contact springs CS₃-CS₆ and theircorresponding insulation displacement connector blades IDC₃-IDC₆.

The impedance of the tracks T₃-T₆ can also be increased byincreasing/maximizing the spacing between track T₄ and track T₅, andbetween track T₃ and track T₆. In one embodiment, the tracks T₄ and T₅diverge from one another as the tracks T₄ and T₅ extend away from thecontact springs CS₄ and CS₅, and then converge again as the tracks T₄and T₅ approach the insulation displacement connector blades IDC₄ andIDC₅. Thus, mid regions of the tracks T₄ and T₅ are spaced relativelyfar away from one another. In one embodiment, a spacing of at least 0.1inches, measured in a direction parallel to a width W of the circuitboard, is defined between portions of the tracks T₄ and T₅. In certainembodiments, this spacing represents at least ¼ of the width of thecircuit board. It will be appreciated that similar spacings can be usedbetween the track T₃ and the track T₆ to increase impedance.

Referring still to FIG. 10, return loss can also be improved byproviding a capacitive coupling C15 between track T₃ and track T₆, and acapacitive coupling C16 between track T₄ and track T₅. For thecapacitive coupling C15 and C16 to improve and not worsen return loss,the couplings C15, C16 should be placed far enough away from the centerof the three zones of compensation Z_(A1)-Z_(A3) so that the phase ofthe capacitance introduced by the couplings C15 and C16 cancels returnloss along the tracks T₃-T₆ at higher frequencies.

FIG. 13 is a graph that depicts how different factors can affect returnloss in the jack across a range of frequencies. In the graph, returnloss is plotted on the y axis and frequency is plotted on the x axis.Line 400 represents the maximum permissible return loss across the rangeof frequencies. Line 402 represents the return loss present in tracksT₃-T₆ if standard 100 Ohm tracks of standard length are used to provideelectrical pathways between the contact springs and the insulationdisplacement connector blades. Line 404 shows the return loss present inthe tracks if the tracks of standard length are converted to highimpedance lines. As shown by line 404, the return loss is improved ascompared to line 402, but still does not comply with the level of returnloss set by line 400. Line 406 shows the return loss in the tracks ifthe high impedance tracks are extended in length between the contactsprings and the insulation displacement connector blades. As shown byline 406, the lengthened, high impedance tracks greatly improve returnloss at lower frequencies, but worsen return loss at higher frequencies(e.g., frequencies greater than 300 MHz). Lines 408A, 408B and 408C showthe effects of adding capacitive couplings C15, C16 between track T₃ andtrack T₆ and between track T₄ and track T₅ in combination with usingrelatively long, high impedance tracks between the contact springsCS₃-CS₆ and the insulation displacement connector blades IDC₃-IDC₆. Tocomply with the return loss levels set by line 400, the distance thecapacitive couplings are placed from the center of the zones ofcompensation Z_(A1)-Z_(A3) is significant. If the capacitive couplingsC15, C16 are too close to the capacitive couplings of the zones ofcompensation Z_(A1)-Z_(A3), the return loss will fail at low frequencies(as shown by line 408A). If the capacitive couplings C15, C16 arepositioned too far from the zones of compensation Z_(A1)-Z_(A3), returnloss failure will occur at higher frequencies as shown by line 408C. Byselecting the distance of the capacitive couplings C15, C16 from thezones of compensation Z_(A1)-Z_(A3) such that the capacitive couplingsC15, C16 effectively cancel return loss for frequencies in the range of200-500 Mhz, the jack can meet the return loss parameters set by line400 over the entire frequency range as shown by line 408B.

FIGS. 14-17 show an example circuit board layout for implementing thecompensation arrangement of FIG. 10. FIGS. 15-17 respectively show thefront, middle and back conductive layers 140, 142 and 144 of the circuitboard 132. FIG. 14 is an overlay of the three conductive layers 140, 142and 144. The circuit board 132 defines openings 301-308 thatrespectively receive posts of the contact springs CS₁-CS₈ so that thecontact springs CS₁-CS₈ are terminated to the board 132. The circuitboard also defines openings 401-408 for respectively receiving posts ofthe insulation displacement connector blades IDC₁-IDC₈ such that theinsulation displacement connector blades IDC₁-IDC₈ are terminated to thecircuit board. Vias extend through the circuit board for electricallyinterconnecting the tracks between the layers 140, 142 and 144. Forexample, vias V_(6A), V_(6B) and V_(6C) interconnect the portions of thetrack T₆ located at the different layers 140, 142 and 144. Also, viasV_(5A) and V_(5B) interconnect the portions of the track T₅ located atthe different layers 140, 142 and 144. Moreover, vias V_(4A) and V_(4B)interconnect the portions of the track T₄ located at the differentlayers 140, 142 and 144. Additionally, via V₃ interconnects the portionsof the track T₃ located at the different layers 140, 142 and 144. Thetracks T₁, T₂, T₇ and T₈ are each provided on a single layer of theboard 132. For example, tracks T₁ and T₂ are provided at layer 140 andtracks T₇ and T₈ are provided at layer 144.

Referring to FIGS. 14-16, the capacitive coupling C1 of the first zoneof compensation Z_(A1) is provided by opposing capacitor plates C1 ₅ andC1 ₃ respectively provided at layers 140 and 142. The capacitivecoupling C2 of the first zone of compensation Z_(A1) is provided byopposing capacitor plates C2 ₄ and C2 ₆ that are respectively providedat the layers 140 and 142. The capacitive coupling C3 of the secondcompensation zone Z_(A2) is provided by opposing capacitor plates C3 ₄and C3 ₃ that are respectively provided at layers 140 and 142. Thecapacitive coupling C4 of the second compensation zone Z_(A2) isprovided by opposing capacitor plates C4 ₅ and C4 ₆ that arerespectively provided at layers 140 and 142. The capacitive coupling C5of the third compensation zone Z_(A3) is provided by opposing capacitorplates C5 _(5A) and C5 _(3A) that are respectively provided at layers140 and 142. The capacitive coupling C5 is also provided byinter-digitated capacitor fingers C5 _(5B) and C5 _(3B) that areprovided at layer 144. The capacitive coupling C6 of the secondcompensation zone Z_(A3) is provided by opposing capacitor plates C6_(6A) and C6 _(4A) respectively provided at layers 140 and 142. Thecapacitive coupling C6 is also provided by inter-digitated capacitorfingers C6 _(6B) and C6 _(4B) provided at layer 144.

The capacitive coupling C7 of the first compensation zone Z_(B1) isprovided by opposing capacitor plates C7 ₁ and C7 ₃ that arerespectively provided at layers 140 and 142 of the circuit board. Thecapacitive coupling C8 of the first compensation zone Z_(B1) is providedby opposing capacitor plates C8 ₂ and C8 ₆ that are respectivelyprovided at the layers 140 and 142 of the circuit board. The capacitivecoupling C9 of the second zone of compensation Z_(B2) is provided byinter-digitated capacitor fingers C9 ₁ and C9 ₆ that are provided atlayer 140 of the circuit board.

The capacitive coupling C10 of the first compensation zone Z_(C1) isprovided by opposing capacitor plates C10 ₅ and C10 ₈ that arerespectively provided at layers 140 and 142 of the circuit board. Thecapacitive coupling C11 of the second compensation zone Z_(C2) isprovided by inter-digitated capacitor fingers C11 ₄ and C11 ₈ that areprovided at layer 144 of the circuit board.

The capacitive coupling C12 of the zone of compensation Z_(D1) isprovided by inter-digitated capacitor fingers C12 ₂ and C12 ₅ providedat layer 140 of the circuit board. The capacitive coupling C13 of thezone of compensation Z_(E1) is provided by parallel capacitor fingersC13 ₈ and C13 ₆ provided at layer 144 of the circuit board. Thecapacitive coupling C14 is provided by inter-digitated capacitor fingersC14 ₅ and C14 ₆ that are provided at layer 144 of the circuit board. Thecapacitive coupling C15 is provided by opposing capacitor plates C15 ₃and C15 ₆ that are respectively provided at layers 140 and 142 of thecircuit board. The capacitive couplings C16 is provided by opposingcapacitor plates C16 ₄ and C16 ₅ that are respectively provided atlayers 140 and 142 of the circuit board.

Referring still to FIGS. 14-17, it is noted that the tracks T₄ and T₅are routed away from one another for a majority of their lengths so asto increase the impedance of the tracks to address return loss.Similarly, tracks T₃ and T₆ are routed away from one another for amajority of their lengths to also increase impedance in the tracks toaddress return loss. It is also noted that tracks T₃-T₆ also preferablyhave extended lengths to increase impedance for improving return lossperformance. For example, referring to FIG. 14, track T₃ loops up andaround as it extends from contact spring CS₃ to its correspondinginsulation displacement connector blade IDC₃. Track T₃ also includes aloop back 900 for further increasing the length of the track T₃. Stillreferring to FIG. 14, track T₄ loops over, up and around as it extendsfrom contact spring CS₄ to its corresponding insulation displacementconnector blade IDC₄. Referring further to FIG. 14, track T₅ loops upand over as it extends from contact spring CS₅ to its correspondinginsulation displacement connector blades IDC₅. Additionally, track T₅has a loop back 902 for further increasing the length of the track.Referring once again to FIG. 14, track T₆ extends over up and around asit extends from contact spring CS₆ to its corresponding insulationdisplacement connector blade IDC₆.

Referring still to FIG. 14, the routing configuration of the tracks onthe circuit board are also adapted for positioning the capacitivecouplings C15 and C16 relatively far from the center of the capacitiveprovided by the three zones of compensation Z_(A1)-Z_(A3). For example,to provide this extra distance, loop extension portions 904 and 906 areprovided with multiple loop backs for increasing the spacings of thecapacitive couplings C15, C16 from the center of the capacitanceprovided by the zones of compensation Z_(A1)-Z_(A3). The circuit boardis also provided with structures adapted for promoting manufacturingefficiency. For example, each set of opposing plate capacitors has afirst plate that is larger than the corresponding second plate so thatportions of the first plate extend outwardly beyond the boundaries ofthe second plate. This facilitates manufacturing efficiency because theexact registration between the plates is not required. Additionally,some of the plates are provided with stubs 910 that can be laser trimmedto exactly tune the capacitance so that the jack satisfies the relevantcrosstalk requirements. The capacitance can also be tuned by using acombination of capacitor plates and parallel capacitor fingers at onezone of compensation. Furthermore, some of the tracks are provided withstubs 912 that can be used during design of the circuit board tomanually vary the lengths of the tracks. In this way, the effect ofvarying certain track lengths can be empirically assessed.

The above specification provides examples of how certain inventiveaspects may be put into practice. It will be appreciated that theinventive aspects can be practiced in other ways than those specificallyshown and described herein without departing from the spirit and scopeof the inventive aspects.

1. A telecommunications jack for use in a twisted pair system, thetelecommunications jack comprising: a housing defining a port forreceiving a plug; a plurality of contact springs adapted to makeelectrical contact with the plug when the plug is inserted into the portof the housing; a plurality of wire termination contacts for terminatingwires to the jack; a circuit board including conductive tracks thatelectrically connect the contact springs to the wire terminationcontacts; and a crosstalk compensation arrangement that providescrosstalk compensation between selected tracks of the circuit board, theselected tracks including two pairs of tracks, wherein tracks of eachpair diverge from one another as the tracks extend from theircorresponding contact spring to their corresponding wire terminationcontacts, the selected tracks also having high impedance portions withimpedances greater than 100 ohms; wherein capacitive couplings areprovided between the tracks of each pair at a position located betweenthe crosstalk compensation arrangement and the wire terminationcontacts, the capacitive couplings being positioned far enough away fromthe crosstalk compensation arrangement to reduce return loss of theselected tracks at least for signal frequencies in the range of 200-500MHz.
 2. The telecommunications jack of claim 1, wherein the highimpedance portions of the selected tracks have impedances greater than150 ohms.
 3. The telecommunications jack of claim 2, wherein the highimpedance portions of the selected tracks extend generally from thecrosstalk compensation arrangement to the wire termination contacts. 4.The telecommunications jack of claim 2, wherein the selected tracksinclude two pairs of tracks, and wherein the crosstalk compensationarrangement includes at least three zones of compensation providedbetween the two pairs of tracks.
 5. The telecommunications jack of claim2, wherein the high impedance portions of the selected tracks havelengths at least 1.5 times as long as straight-line distances betweenthe contact springs and the wire termination contacts.
 6. Thetelecommunications jack of claim 2, wherein the high impedance portionsof the selected tracks have lengths at least 2 times as long asstraight-line distances between the contact springs and the wiretermination contacts.
 7. The telecommunications jack of claim 2, whereinthe high impedance portions of the selected tracks have lengths at least3 times as long as straight-line distances between the contact springsand the wire termination contacts.
 8. The telecommunications jack ofclaim 2, wherein the high impedance portions of the selected tracks haveloop-back portions located between the crosstalk compensationarrangement and the wire termination contacts for increasing the lengthsof the high impedance portions.
 9. The telecommunications jack of claim8, wherein the loop-back portions have a serpentine configuration. 10.The telecommunications jack of claim 2, wherein: the plurality ofcontact springs includes first, second, third, fourth, fifth, sixth,seventh and eighth consecutively arranged contact springs adapted tomake electrical contact with the plug when the plug is inserted into theport of the housing; the plurality of wire termination contacts includesfirst, second, third, fourth, fifth, sixth, seventh and eighth wiretermination contacts for terminating wires to the jack; the circuitboard includes first, second, third, fourth, fifth, sixth, seventh andeighth tracks that respectively electrically connect the first, second,third, fourth, fifth, sixth, seventh and eighth contact springs to thefirst, second, third, fourth, fifth, sixth, seventh and eighth wiretermination contacts; a first compensation zone is provided includingfirst and second capacitive couplings, the first capacitive couplingbeing made between the third and fifth tracks and the second capacitivecoupling being made between the fourth and sixth tracks; a secondcompensation zone is provided including third and fourth capacitivecouplings, the third capacitive coupling being made between the thirdand fourth tracks and the fourth capacitive coupling being made betweenthe fifth and sixth tracks; a third compensation zone is providedincluding fifth and sixth capacitive couplings, the fifth capacitivecoupling being made between the third and fifth tracks, and the sixthcapacitive coupling being made between the fourth and sixth tracks; andthe selected tracks include the third, fourth, fifth and sixth tracks.11. The telecommunications jack of claim 10, wherein the high impedanceportions of the selected tracks have lengths at least 1.5 times as longas straight-line distances between the contact springs and the wiretermination contacts.
 12. The telecommunications jack of claim 10,wherein the high impedance portions of the selected tracks haveloop-back portions located between the crosstalk compensationarrangement and the wire termination contacts for increasing the lengthsof the high impedance portions.
 13. The telecommunications jack of claim10, wherein capacitive couplings are provided between the fourth andfifth tracks and between the third and sixth tracks at positions locatedbetween the crosstalk compensation arrangement and the wire terminationcontacts, the capacitive couplings being positioned to reduce the returnloss of the selected tracks at least for signal frequencies in the rangeof 200-500 MHz.
 14. The telecommunications jack of claim 1, wherein thehigh impedance portions of the selected tracks have impedances greaterthan 175 ohms.
 15. A telecommunications jack for use in a twisted pairsystem, the telecommunications jack comprising: a housing defining aport for receiving a plug; a plurality of contact springs adapted tomake electrical contact with the plug when the plug is inserted into theport of the housing; a plurality of wire termination contacts forterminating wires to the jack; a circuit board including conductivetracks that electrically connect the contact springs to the wiretermination contacts, the conductive tracks including first and secondpairs of tracks adapted for carrying twisted pair signals, the firstpair of tracks including first and second tracks, and the second pair oftracks including third and fourth tracks; a crosstalk compensationarrangement that provides crosstalk compensation between the first pairof tracks and the second pair of tracks; and capacitive couplings forreducing the return loss of the first and second pairs of tracks, thecapacitive couplings including a first capacitive coupling between thefirst and second tracks and a second capacitive coupling between thethird and fourth tracks, the first and second capacitive couplings beingpositioned far enough away from the crosstalk compensation arrangementto reduce the return loss of the first and second pairs of tracks atleast for signal frequencies in the range of 200-500 MHz.
 16. Thetelecommunications jack of claim 15, wherein the plurality of contactsprings includes eight contact springs consecutively arranged inpositions one, two, three, four, five, six, seven and eight, wherein thefirst pair of tracks correspond the contact springs located at positionsfour and five, and the second pair of tracks correspond to the contactsprings located at positions three and six.
 17. The telecommunicationsjack of claim 15, wherein the first capacitive coupling is formedbetween first and second spaced-apart capacitor plates, and the secondcapacitive coupling is formed between third and fourth spaced-apartcapacitor plates.
 18. A method for compensating for crosstalk and returnloss in a conductive pair adapted for carrying a twisted pair signal,the conductive pair including first and second conductive tracks, themethod comprising: applying crosstalk compensating capacitances to thefirst and second conductive tracks at one or more zones of compensationto reduce crosstalk; and applying a return loss compensating capacitancebetween the first and second tracks at a position far enough away fromthe crosstalk compensation arrangement to reduce return loss.